AST 5100 Coilovers Explained: Street, Street Performance And Clubracing
AST, family by family
The 5100 is where most AST customers will land, and it is the part of the range that takes the most explaining: 296 listings, one damper, and three packages built around it.
Cameron's shortcut is to ignore the damper completely for the first five minutes. It is the same 12 click rebound unit in every box. What you are choosing is the hardware around it: the top mounts, and whether the rear spring sits on the damper or next to it. Garreth adds the question nobody asks until the car is on the ramp. Do you want to change the camber?
Here is what each package includes, the inverted and non-inverted versions, how to set the adjuster, and the notes our listings carry.
- One damper in every 5100: monotube, 12 position rebound adjuster
- Ride height on a threaded body, so it adjusts without changing spring preload
- Street uses your original top mounts
- Street Performance adds camber-adjustable front top mounts
- Clubracing adds solid rear top mounts and a coilover rear
- Inverted on most strut cars, non-inverted on wishbone cars and some others
- AST starts you at click 6 and says move one or two at a time
Three packages around one damper
| Package | Front top mounts | Rear top mounts | Rear layout on our listings | Listings | From |
|---|---|---|---|---|---|
| 5100 Street | Your original ones | Your original ones | 70 divorced, 48 coilover | 118 | £1,728 |
| 5100 Street Performance | Camber-adjustable, included | Your original ones | 34 divorced, 62 coilover | 96 | £2,508 |
| 5100 Clubracing | Camber-adjustable, included | Solid, included | All 82 coilover | 82 | £2,880 |
"Where applicable" applies throughout: top mounts are included where the car has a design for them. Prices are the lowest listing today, inc VAT.
The steps between them are fairly regular. For the same car, Street Performance typically costs £564 more than the inverted Street kit, and Clubracing £396 more again. Those are medians across the cars that have both, 64 and 67 of them. The jump from Clubracing to a 5200 2-way is bigger, typically £1,596, because that is where the reservoirs and the second adjuster arrive.
5100 Street
AST pitches the Street package at one question: do you want the best road balance for everyday use? It keeps your original top mounts, comes with springs, and on most cars keeps the rear spring where the factory put it. AST sets those rear rates for the car and they are fixed, one spring option for the rear axle. The initial settings and rates come from AST's own development for the application.
That makes it the simplest fit of the three, with nothing new at the top of the strut and nothing to set up for camber, and the car keeps its factory ride quality character with a better damper under it.
5100 Street Performance
Street Performance is the Street package plus camber-adjustable front top mounts. AST adjusts camber on its mounts with four bolts, and describes the bearings as the same materials used in aviation, almost free of maintenance. They are pillowball mounts, so you feel more of the road through the steering.
Camber is the reason to buy it. A lowered car often wants more negative camber at the front than its factory mounts allow, and a car that sees a track wants more again. The rear is still divorced on many of these kits, with the same fixed rear rates as Street.
5100 Clubracing
Clubracing is a coilover at all four corners, with camber front and solid rear top mounts included where the car allows. AST writes it for someone using the car on track, or after both track performance and a road balance for daily driving. AST's own page heads it 5100 Competition.
The coilover rear is the real difference: with the spring on the damper you can change spring rates at the back, which you cannot do on a divorced Street kit, and the solid rear mounts take out the rubber that lets a rear axle move around under load.
A few of the cars we expect to be asked about most, across all three packages:
Inverted and non-inverted
Of the 118 Street listings, 84 are inverted kits with part numbers starting ACU, and 34 are non-inverted, starting ACS, ACA, ADA or RUV. Street Performance and Clubracing are inverted on almost every car. All of them share the same 12 click adjuster.
The inverted 5100 front is a 44.5mm strut body with a 14mm piston rod inside it. Turning a strut upside down puts the large diameter where the side load is, which is why AST uses it on MacPherson cars. The non-inverted damper is the one AST sold as the 4100: a 22mm shaft strut with a steel body. AST fits it to double wishbone cars as standard, and several set descriptions on our listings still call it 4100.
Some strut cars appear with both versions, a few pounds apart. The E46 M3 is one: ACU-B1103SD is inverted, ACS-B1103SD is not. The first line of each listing says which it is.
Cameron and Garreth split on this one. Cameron takes the inverted kit on a strut car every time, on the side load argument. Garreth points out that AST describes the inverted 5100 as upgradeable to 5300 specification later, which it never did for the 4100, and for him that settles it on any car that might see a track.
Setting the rebound adjuster
The adjuster has 12 positions and is marked plus and minus; turning towards plus firms it up. Inside, it opens and closes a small bleed that lets oil past the piston. AST builds a blow off valve into the rebound side so the rebound setting interferes as little as possible with compression.
- Start at 6. AST's manual gives the middle position as the starting point, front and rear
- One or two clicks. Move one or two at a time and drive it before moving again
- Where the knob is. On inverted fronts it sits at the bottom of the strut; on most rears it is on top of the piston rod
- Height is separate. The threaded body sets ride height without touching spring preload
Garreth’s advice to anyone setting a car up for the road is not to chase the extremes: find the setting the car likes on your roads, write it down, and go firmer for a trackday by a couple of clicks.
Which cars the 5100 covers
| Make | Street | Street Performance | Clubracing |
|---|---|---|---|
| BMW | 29 | 22 | 24 |
| Porsche | 12 | 14 | 12 |
| Honda | 8 | 10 | 9 |
| Subaru | 7 | 7 | 7 |
| Mini | 7 | 8 | 6 |
| Ford | 8 | 6 | 6 |
| Renault | 7 | 8 | 0 |
| Audi | 9 | 3 | 2 |
| Mitsubishi | 4 | 4 | 4 |
| Mazda | 4 | 4 | 3 |
| Volkswagen | 4 | 3 | 3 |
| Nissan | 3 | 3 | 4 |
| Toyota | 2 | 2 | 5 |
| Mercedes | 6 | 2 | 0 |
Listings naming each make, the fourteen deepest. The whole range is on the AST 5100 category page.
Not every car gets every package. Lotus gets the non-inverted Street kit only in the 5100 range. The Honda Civic Type R FK8 and FL5 go straight to Clubracing, with no Street kits. Renault has no Clubracing kit at all, and neither do the Porsche 944 and 968.
Notes our 5100 listings carry
- Body work for top mounts. 11 of our 5100 listings say the body needs modifying when the front top mounts are used, mostly VW Group and Renault
- Spacers with original wheels. 9 MINI listings ask for a 5 to 10mm front spacer to run the original wheels
- EDC. BMWs with electronic damping need a delete kit, ordered separately
- 3 bolt or 5 bolt. BMW M cars list their top mount pattern, and the kit follows it
- LCI. BMW listings split pre and post facelift, and the two are different kits
- Wheel PCD. The Impreza kits split on 5x100 and 5x114.3
No preload on arrival
AST ships kits with zero spring preload. Set it before the car is lowered and keep at least 5mm between spring and tyre.
Alignment
Lowering changes toe and camber. Have the alignment done once the car has settled, and again if you move the ride height much.
Rebuildable
Every inverted 5100 can be rebuilt and revalved. The UK service centre is Racesport, near Brackley.
Common questions
Is the 5100 fixed damping?
No, although some retailers describe it that way. Every 5100 has a 12 position rebound adjuster, and the knob is on every kit we list.
Is the 4100 the same as the 5100?
No. The 4100 was AST’s non-inverted damper and the 5100 its inverted one. AST now sells the non-inverted kits under the 5100 Street heading, which is why some descriptions still say 4100.
Can I add camber plates to a Street kit later?
AST sells top mounts separately, and Street Performance is simply Street with them included. Ask us for the part numbers for your car, and check whether the body needs modifying for them.
Can I change the rear spring rate on a Street kit?
Not on a divorced rear. AST fixes the rear rate per car on those kits. Clubracing, with a coilover rear, lets you change it.
Can a 5100 become a 5300 later?
AST describes the inverted 5100 as fully upgradeable to 5300 specification. Talk to us about your exact kit first.
Will a 5100 Street ride harshly on the road?
It is built for road balance, with the rebound adjuster to tune it. Start at 6 and move one or two clicks at a time until the car suits your roads.
Which one we would buy
For a road car, Cameron buys Street and spends the difference on an alignment and good tyres. Once camber comes into it, and on most lowered cars it does, Street Performance earns its money quickly.
Garreth would go straight to Clubracing for anything that does more than two or three trackdays a year. Solid rear mounts, a coilover rear he can re-spring, and the same damper he could have had anyway. His one caveat is the car that also has to do the school run. That car keeps its rubber rear mounts.
The AST range guide shows where the 5100 sits against the 5200 and 5300, and the MOTON guide covers the sister brand. Send us the registration and we will find your part number.
Manufacturer reference: AST 5100 Street Performance and AST Clubracing. Shop the AST 5100 range.
The rest of the AST and MOTON series: AST Suspension explained, MOTON Suspension explained.
Send us both part numbers and the registration. We will explain the difference for your car and check the top mounts, EDC and any body work before you order.
Send the registration or VIN and tell us whether camber matters to you and whether the car sees a track. We will pick the package and part number with you, including the inverted or non-inverted question where your car has both.
